QTableView Drag and Drop

[PeterPan32]

Hi everybody,
I want to realize following issue with two TableViews:

• TableView A and TableView B have a different type of data
• The user shall be able to reorder the elements of B (! without overwriting existing data-sets !)
• The user shall be able to drag elements from A to B (data-set must be "converted" of course)

I thought that can't be so difficult...
Currently I have problems with step 2 (reorder elements), because if I move on row over another the other row will be overwritten.

Code for Table A:

//selection behavior
    tableViewA->setSelectionBehavior(QAbstractItemView::SelectRows);
    tableViewA->setSelectionMode(QAbstractItemView::SingleSelection);
//drag and drop
    tableViewA->setDragEnabled(true);
    tableViewA->setDropIndicatorShown(true);
    tableViewA->setDragDropMode(QAbstractItemView::InternalMove);
    tableViewA->setDragDropOverwriteMode(false);

Thank you for your help.

[Xicor]

usually when i do stuff like this i will subclass and modify the drag drop events/signals/slots to do what i want them to do.

[PeterPan32]

Thank you.
I'm new to Qt. Do you have an example or something like that?

[Ratzz]

@PeterPan32
May be this helps you http://doc.qt.io/qt-4.8/dnd.html.

[PeterPan32]

I decided first to read the article about Model/View Programming (http://doc.qt.io/qt-5.5/model-view-programming.html).
There is a simple dnd example. I tried it but it doesn't work. Either the example or me is wrong.
Here is my code of the main function:

#include "stringlistmodel.h"
#include <QApplication>
#include <QListView>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QStringList list({"a","b","c","d","e","f"});
    StringListModel *model = new StringListModel(list);
    QListView *view = new QListView();
    view->setModel(model);
    view->setSelectionMode(QAbstractItemView::SingleSelection);
    view->setDragDropMode(QAbstractItemView::InternalMove);
    view->setDragEnabled(true);
    view->setAcceptDrops(true);
    view->setDropIndicatorShown(true);
    view->show();

    return app.exec();
}

stringlistmodel.h:

#include <QAbstractListModel>
#include <QStringList>

class StringListModel : public QAbstractListModel
{
    Q_OBJECT
public:
    StringListModel(const QStringList &strings, QObject *parent = 0);


    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    QVariant data(const QModelIndex &index, int role) const;
    QVariant headerData(int section, Qt::Orientation orientation,
                        int role = Qt::DisplayRole) const;

    Qt::ItemFlags flags(const QModelIndex &index) const;

    bool insertRows(int position, int rows, const QModelIndex &index = QModelIndex());
    bool removeRows(int position, int rows, const QModelIndex &index = QModelIndex());

    Qt::DropActions supportedDropActions() const;

private:
    QStringList stringList;
};

stringlistmodel.cpp:

#include "stringlistmodel.h"

StringListModel::StringListModel(const QStringList &strings, QObject *parent)
    : QAbstractListModel(parent), stringList(strings)
{
}

int StringListModel::rowCount(const QModelIndex &parent) const
{
    return stringList.count();
}

QVariant StringListModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();

    if (index.row() >= stringList.size())
        return QVariant();

    if (role == Qt::DisplayRole)
        return stringList.at(index.row());
    else
        return QVariant();
}

QVariant StringListModel::headerData(int section, Qt::Orientation orientation,
                                     int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();

    if (orientation == Qt::Horizontal)
        return QString("Column %1").arg(section);
    else
        return QString("Row %1").arg(section);
}

Qt::ItemFlags StringListModel::flags(const QModelIndex &index) const
{
    Qt::ItemFlags defaultFlags = QAbstractListModel::flags(index);

    if (index.isValid())
        return Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled | defaultFlags;
    else
        return Qt::ItemIsDropEnabled | defaultFlags;
}

bool StringListModel::insertRows(int position, int rows, const QModelIndex &parent)
{
    beginInsertRows(QModelIndex(), position, position+rows-1);

    for (int row = 0; row < rows; ++row) {
        stringList.insert(position,"");
    }

    endInsertRows();
    return true;
}

bool StringListModel::removeRows(int position, int rows, const QModelIndex &parent)
{
    beginRemoveRows(QModelIndex(), position, position+rows-1);

    for (int row = 0; row < rows; ++row) {
        stringList.removeAt(position);
    }

    endRemoveRows();
    return true;
}

Qt::DropActions StringListModel::supportedDropActions() const
{
    return Qt::MoveAction | Qt::CopyAction;
}